1. Field of the Invention
The present invention relates generally to a heat dissipation structure, and more particularly to a bearing cooling structure and a fan with the bearing cooling structure.
2. Description of the Related Art
The bearing of a conventional fan is often fixed in several manners as follows:    1. A prior art discloses a metal bearing cup fan motor fixing structure. The fan includes a frame body, a circuit board disposed on the frame body, a stator assembly fixed on the frame body and a rotor assembly shafted around the stator assembly. A rest seat is disposed at the center of the frame body. A bearing sleeve is disposed on the rest seat. The bearing sleeve is composed of a fitting section and a hollow tubular body. More than one connection section is disposed on the outer circumference of the fitting section. A lower winding support is fixedly disposed under the bottom of the stator assembly. The lower winding support is formed with a central through hole. More than one engagement section is disposed on the inner circumference of the through hole. The engagement sections are correspondingly engaged with the connection sections of the bearing sleeve. Accordingly, the stator assembly can be securely disposed on the bearing sleeve of the rest seat by means of the lower winding support. Even after a long period of use, the stator assembly is still prevented from loosening or detaching under external force. Therefore, the operation of the fan will not be affected.    2. A prior art discloses a nonmetal bearing cup fan motor fixing structure. The fan includes a frame body, a circuit board disposed on the frame body, a stator assembly fixed on the frame body and a rotor assembly shafted around the stator assembly. A rest seat is disposed at the center of the frame body. A bearing sleeve is disposed on the rest seat. The bearing sleeve is composed of a fitting section and a hollow tubular body. The fitting section integrally protrudes from the center of the rest seat. More than one connection section is disposed on the outer circumference of the fitting section. More than one rib is disposed on the outer circumference of the hollow tubular body. A lower winding support is fixedly disposed under the bottom of the stator assembly. The lower winding support is formed with a central through hole. More than one engagement section is disposed on the inner circumference of the through hole. The engagement sections are correspondingly engaged with the connection sections of the bearing sleeve. Accordingly, the stator assembly can be securely disposed on the bearing sleeve of the rest seat by means of the lower winding support. Even after a long period of use, the stator assembly is still prevented from loosening or detaching under external force. Therefore, the operation of the fan will not be affected.    3. A prior art discloses a fan bearing cup structure including fan frame having a rest section at the center. A bearing cup is disposed on the rest section. More than one engagement unit is disposed on outer circumference of the bearing cup in proper position. A motor unit having a central through hole is fitted around the bearing cup. The inner wall face of the through hole are formed with recesses for correspondingly engaging with the engagement unit. A fan impeller unit is composed of a hub, a shaft, blades and magnetic bodies. The shaft is disposed at the center of the hub and fitted in the bearing cup. The magnetic bodies are disposed on inner circumference of the hub corresponding to the motor unit. Accordingly, the motor unit can be securely disposed on the bearing cup without leftward or rightward loosening or rotating or displacing or upward detaching from the bearing cup.    4. A prior art discloses a motor including a sleeve, a stator seat and a rotor structure. At least one first connection section is disposed at top end of the sleeve. The stator seat has a lining formed with a central hole. The sleeve is fitted in the central hole of the stator seat. At least one second connection section is disposed on the circumference of the central hole of the lining of the stator seat corresponding to the first connection section of the sleeve. The second connection section is connected with the first connection section by means of thermal welding. The rotor structure has a rotary shaft disposed in the sleeve.
The above conventional bearing fixing techniques can be substantially classified into plastic injection molding and metal press. With respect to metal press, the metal has higher heat conductivity so that the heat of the bearing can be dissipated at higher efficiency to more quickly lower the temperature of the bearing. However, the cost for such measure is higher. On the other hand, the cost for the plastic injection molding is lower. However, the plastic can hardly effectively conduct the heat of the bearing to outer side so that the heat dissipation effect is poor. As a result, the temperature of the bearing may rise to deteriorate the performance.
It is therefore tried by the applicant to provide a bearing cooling structure, which not only is manufactured at lower cost, but also is able to efficiently conduct the heat of the bearing to outer side.